JAXB在解组后创建空的TreeSet

Question

我有一个RESTful服务客户机。服务返回SortedSet<Movie>，其中Movie是带注释的类。生成的XML如下所示。

在客户端，我有一个自定义的MessageBodyReader，如下所示。问题是Unmarshaller总是返回一个空的TreeSet。

MovieSetMessageBodyReader.java

@SuppressWarnings("unchecked")
@Override
public TreeSet<Movie> readFrom(Class<TreeSet<Movie>> type,
    Type genericType, Annotation[] annotations, MediaType mediaType,
    MultivaluedMap<String, String> httpHeaders, InputStream entityStream)
    throws IOException, WebApplicationException {
Class<Movie> baseType = Types.getCollectionBaseType(type, genericType);

try {
    JAXBContext ctx = JAXBContext.newInstance(type, baseType);
    JAXBElement<?> element = ctx.createUnmarshaller().unmarshal(
        new StreamSource(entityStream), type);

    return (TreeSet<Movie>) element.getValue();
} catch (JAXBException e) {
    e.printStackTrace();
}

return null;
}

MovieServiceRestEasyClient.java

@GET
@Consumes("text/xml")
public SortedSet<Movie> sendRequestByProxy() {
Map<String, Object> requestAttributes = new HashMap<String, Object>();
requestAttributes.put("path", path);

MovieServiceRestEasy proxy = ProxyFactory.create(
    MovieServiceRestEasy.class, ENDPOINT, requestAttributes);
ClientResponse<TreeSet<Movie>> response = (ClientResponse<TreeSet<Movie>>) proxy
    .getMovieSet(path);
return response.getEntity(TreeSet.class, (new GenericType<TreeSet<Movie>>() {}).getGenericType());

}

XML：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<collection>
<movie>     
    <genre>Unknown</genre>
    <name>4.3.2.1</name>
    <year>2010</year>
</movie>
<movie>     
    <genre>Unknown</genre>
    <name>Battlestar Galactica The Plan</name>
    <year>2009</year>
</movie>
</collection>

Answer 1

为什么不使用POJO来保存未编组/编组的值呢？例如：

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;


@XmlRootElement( name = "movie" )
public class Movie
{
    @XmlElement
    String name;

    @XmlElement
    String genre;